The invention relates to the uniform cooling of such articles as a hot, cast, rolled, or extruded generally circular metal workpiece, such as a billet, a rod, a bar or a tube, issuing from a continuous caster, a hot rolling mill, or an extrusion press, respectively. More particularly, it relates to an apparatus and a method where several curtain walls of coolant are applied to the outer peripheral surface of the workpiece along a horizontal passline between the rolling mill stands and/or at the runout section, or where coolant is applied to the extruded workpiece immediately as it leaves the die.
As is well-known in the art, coolant is applied to control the finishing temperature of a workpiece. It also acts to suppress oxide formation at various stages of the rolling process including coiling, or gathering thereof.
Several types of cooling systems and methods are presently being practiced for the cooling of hot rolled rod or bar after the last rooling stand of a finishing train or after the extrusion process in the runout section. As disclosed in U.S. Pat. No. 4,084,798, one type involves a number of open ended, tandemly arranged troughs having slots for directing streams of water onto the workpiece. Another type involves a series of boxes containing high pressure water sprays for cooling rod or bar as it passes therethrough. Another system involves a plurality of tandemly arranged cooling tubes containing water in which the workpiece is immersed and through which it travels.
All of these above systems have several severe disadvantages, which are non-uniform cooling, limited cooling capacity, and poor efficiency in terms of the quantity of water used per unit of heat removed in the available space which may result in low production. The workpiece is not uniformily or efficiently cooled along the outer surface of the workpiece, often resulting in a non-uniform microstructure, and thus, non-uniform metallurgical characteristics and physical properties. Also, due to the non-uniform and less efficient cooling, the oxide formation varies and unacceptable surface conditions exists.
Another disadvantage of prior systems becomes very evident in the increased speeds in which the workpiece to be cooled travels in modern mills and presses, and the time it takes for the workpiece to reach its required temperature. These considerations require that the runout section, usually consisting of several sprays and/or troughs and tubes, extend a considerable distance thereby occupying a substantial amount of plant area.
Spray units may be positioned between the roughing, intermediate, and finishing trains and/or the stands thereof to control the temperature of a hot rolled workpiece. U.S. Pat. No. 3,889,507 illustrates a water cooling apparatus positioned between mill trains, and containing several spray nozzles arranged to apply coolant longitudinally and onto the circumference of a workpiece. Here, again, it can be shown that, in addition to the well-known inefficiencies of high pressure spray systems, a non-uniform cooling on the surface will occur. Since several spray nozzles are needed to obtain the desired cooling effect, this apparatus in the aforesaid '507 patent extends a substantial length. In some instances, several water cooling apparatuses may be necessary, thereby occupying a great amount of space. It is also to be noted that this '507 patent sets forth another disadvantage inherent with troughs and tubes in that since vapor blankets form around the metal, the cooling efficiency of the water is greatly reduced.
It is an object of the present invention to provide an apparatus to optimize the rate of cooling to produce a finishing temperature of a heated, solid generally round metal workpiece which will give a desirable microstructure, reduce the growth of surface oxides, and improve surface conditions, and to achieve this by occupying an area substantially smaller than that required by previous cooling systems.
It is a further object of the present invention to provide an apparatus at the runout section of a mill or press, and/or between stands in a mill which will deliver curtain walls of coolant which evenly cool a round, heated metal workpiece so that a more desirable microstructure is obtained in the workpiece in the case of a runout section, and an increased production rate is obtained in the instance of having the apparatus located between stands.
A further object of the present invention is to provide an annular header having a center opening through which a workpiece travels, and which has several, evenly spaced nozzles each having an elongated opening extending parallel to the path of travel of the workpiece and each located radially relative to the workpiece, for delivering low pressure curtain walls of coolant along a longitudinal portion of the workpiece.